ADSORPTION OF TUNGSTEN ON STEPPED TUNGSTEN SURFACES STUDIED BY WORK FUNCTION MEASUREMENT.

Work function measurements have been performed during the deposition of W on the (110)W plane and several stepped W surfaces with (110) terraces and different terrace width. For each sample the work function decreases with growing coverage. The total work function drop diminishes strongly with decreasing terrace width. The results are interpreted in terms of a reduced nucleation process on stepped surfaces as compared to the flat (110) plane. The step edges act as sinks for the deposited adatoms and cause in their proximity a ″dead″ zone for nuclei formation. Details of the work function change with coverage are discussed in terms of an edge roughening effect on stepped surfaces.